Long-Term Coastal Fish Community Dynamics in the Michigan Waters of the Great Lakes

Ecosystem changes have likely increased the importance of coastal ecosystems (<30 m depth) to lake-wide dynamics across the Great Lakes, but less is known about coastal habitats relative to offshore habitats.  We evaluated spatial and temporal dynamics of coastal fish communities in the Michigan waters of the Great Lakes, focusing on Lakes Huron and Michigan.  Using multiple long-term gillnet surveys maintained by the Michigan Department of Natural Resources, we assessed the dynamics of fish community composition, metrics of species diversity, and catch-per-unit-effort (CPUE) of key fish species across space and time.  Permutation multivariate analyses of variance demonstrated significant differences in the composition of fish communities between sites. Nonmetric multidimensional scaling suggests this is primarily driven by differences between exposed coastlines and embayments.  Within each habitat type, latitude, temperature, and eutrophication tolerance guild appear to drive dissimilarity in fish communities among sites.  In general, significant trends in species richness and CPUE of key fish species were uncommon, but when present, the directionality of trends was inconsistent across sites.  These results highlight that fish communities in coastal habitats are highly heterogeneous and researchers and managers should use caution when extrapolating results from one area to broader scales.